The previous definition, in effect since 1994, said adults needed to have at least six of a possible nine symptoms from either of two categories. The symptoms include the inability to focus on tasks, fidgeting, and interrupting others. The new definition reduced it to five of the nine.

It also increased the age at which some of those symptoms first must have been present -- from before age 7 to before age 12.

Seventy-eight percent of those among the work group of experts who oversaw the changes had financial ties to the pharmaceutical industry, according to a 2012 analysis by the journal PLoS Medicine.

Psychiatrist Darrel Regier MD, MPH, a spokesman for the American Psychiatric Association, said financial conflicts were limited to $10,000 a year in income such as working as industry consultants, advisers, and speakers.

Regier, who served as vice chairman of the diagnostic manual's task force, defended the inclusion of adult ADHD in the document. He said that while it was once thought that children would age out of the disorder, for some, it remains in adulthood.

"Is it believable that this one mental disorder is one that kids would totally outgrow?" he said. "I think not."

Finally, the cumulative result of these factors was as expected: Prescriptions spiked.

At the same time, the growing focus on adult ADHD prompted questions from skeptics:

How valid was the diagnosis?

How many people are truly impaired?

What role does promotion by drug-makers have in the rapidity of ADHD diagnoses?

Has the spike in prescriptions for ADHD caused more harm than good?

"It is very easy to fake the symptoms of ADHD," said Daniel Carlat, MD, a psychiatrist at Tufts University School of Medicine and author of Unhinged: the Trouble with Psychiatry, a Doctor's Revelation about a Profession in Crisis.

According to the medical literature, the prevalence of ADHD in adults is about half that in children.

For years, the legitimacy of the adult ADHD was based on the belief that it was a condition that started in childhood and, for some, persisted into adulthood.

But last year that hypothesis was shaken by the publication of a provocative, long-term study that began in the early 1970s and followed more than 1,000 New Zealand children until age 38.

In that study Terrie Moffitt, PhD, a psychologist at Duke University, and her colleagues found that in childhood, 6% of those in the study had ADHD. At age 38, that number had dropped to 3%.

And the biggest surprise was the lack of evidence of significant overlap between the two groups.

Only 5% of those with ADHD in childhood still met the criteria at age 38. And only 10% of those who met the definition at age 38 were among those with the condition in childhood.

ADHD or Something Else?

That, in turn, led the researchers to speculate that some of the adult patients were substance abusers who had attention problems stemming from drugs and alcohol, and that others may have had a personality disorder and were trying to game the system to obtain stimulants to abuse.

Moffitt noted that while childhood ADHD is considered a brain development condition, adult ADHD patients in her study scored normally on neuropsychological tests.

"It seems to be a different disorder," Moffitt said.

Adults with ADHD may have trouble completing tasks, prioritizing, and keeping appointments. Some research even shows a connection between the condition and higher rates of divorce, unemployment, and car accidents.

However, those only are associations, not proof that ADHD causes the problems or -- more importantly -- that ADHD drugs will prevent them.

In 2014, the pharmaceutical company Shire paid $56 million to settle a U.S. Department of Justice allegation that it illegally promoted Vyvanse and two other ADHD drugs, Adderall XR, and Daytrana.

Between 2007 and 2010, according to the Justice Department, company sales representatives claimed Vyvanse would prevent car accidents, divorce, arrests, and unemployment.

In an email, Shire spokesperson Charlie Catalano said adult ADHD is a real and distinct medical condition.

He said the company has a heritage of providing medicines to underserved patient populations such as people living with ADHD "who have very real medical needs and where additional treatment options can make an immediate and life-altering difference."

"Our medications are proven to be effective when used according to prescribing practices of a licensed, trained health care professional," he said.

Drug industry exuberance for the budding adult ADHD market was highlighted in a 2008 report from the market research firm Datamonitor that serves the worldwide pharmaceutical industry.

"Estimated to be twice the size of the pediatric ADHD population, the highly prevalent, yet largely untapped, adult ADHD population continues to represent an attractive niche to target," the report said.

From 2008 to 2012, prescriptions of ADHD drugs to adults increased 53%, according Express Scripts, a national prescription benefit plan provider.

Overall, ADHD drugs now are one of the most lucrative sectors of the U.S. drug market, totalling more than $10 billion in sales and 83 million prescriptions in 2014 , according to data from IMS Health, a drug market research firm.

One of the authors, British psychiatrist Joanna Moncrieff, MD, said there may be a small number of adults who are hyperactive and find it difficult to concentrate.

But, she added, "Diagnostic criteria are so loose that anyone could qualify."

More importantly, Moncrieff said, there is not good evidence that using stimulant drugs does any more than provide modest improvement on rating scales of how users rate their performance on measures such as concentration and organization. She noted that any benefit likely is influenced by the fact that the drugs also make people feel good.

Moncrieff, of University College London, said the boom in adult ADHD cases increases the likelihood of a repeat of the prescription stimulant epidemic in the 1960s, when the pills were marketed for weight loss.

For decades, stimulants have been known for the ability to improve alertness and focus for users ranging from pilots to college students.

But they also are powerful enough to produce a sense of euphoria in adults, making them a popular for drug abusers.

In 2014, about 1 million people 26 and older used prescription stimulants for nonmedical purposes, which includes using a drug without a prescription or using a drug for the feeling it causes, according to data from the most recent National Survey on Drug Use and Health survey.

Increasingly, those and other overuse problems have been playing out in hospital emergency rooms.

Between 2005 and 2010 -- more recent numbers were not available -- emergency room visits involving ADHD drugs more than doubled, from 13,379 to 31,244, according to data from Substance Abuse and Mental Health Services Administration.

The vast majority of those cases involved adults.

One Adult's Story

Katie Erickson, 35, never made it to the emergency room. On May 17 last year, her friends found her dead in her Milwaukee apartment.

Erickson, a psychiatric nurse who worked with children, had been taking Vyvanse for ADHD.

Her father, Ron Erickson, said he was not sure when she was diagnosed with the condition but it may have been when she was in nursing school during her late 20s.

Erickson said he and his wife, Barbara, wondered whether their daughter really needed the prescription, but Katie was an independent person and was private about certain things.

"To us, it almost seemed like she was getting more nervous on it, a little shaky," he said.

To friends, Katie occasionally would joke about how the condition made it hard for her to pay attention.

The night before she died she had been out with friends celebrating getting a new nursing job.

At a bar, the friends noticed she was sweating profusely, acting hyper and seemed out of it, according to the medical examiner's report, which listed Katie's immediate cause of death was an accidental, acute drug mixture of amphetamine, a narcotic painkiller, and alcohol.

Those who knew her were shocked.

"She was very smart," said a friend, who also is a nurse and who asked not be named for this story because of her job. "She was not new to these medications. She worked with them."

The friend, who was one of those who found Erickson dead, said her story is a caution to others who use potentially dangerous prescription drugs.

"I don't think Katie was an addict," she said. "Our entire group of girls, we like to have fun; we like to go out, but I don't think we thought anything like this would ever happen to any of us."

People who are prescribed the drugs need to be careful with how they use them and friends need to be more observant, she said.

"Maybe if we were just paying more attention, maybe somebody could have stayed with her that night," she said.

While the potential for harm and abuse of prescription stimulants is well known, little rigorous research has weighed the long-term benefit-versus-harm of giving adults the drugs.

Most of the drugs that are approved for use in adults only have been tested in clinical trials lasting a few weeks or months. In practice, they are often used for many months or years.

Vague Definition Means Big Potential

However, California psychiatrist Lawrence Diller, MD, author of the book Running on Ritalin, argues the official definition in DSM provided a vague justification for overprescribing. He said he believes amphetamines, which have been around since the 1930s, are "dangerously over prescribed" in adult ADHD.

"If you don't study history, you are doomed to repeat it," he said. "We have had multiple waves since 1929 of doctor prescribed stimulant abuse epidemics."

Diller said there is little doubt ADHD has caused impairment for some adults, but says many others -- including two of his former patients -- have been able to get diagnosed because they feel they need the drugs to attain some career goal.

One was a man in his 50s who worked for a Wall Street firm and felt he needed the drugs to keep up with new job responsibilities. He took the drugs for a while, but eventually retired and stopped using them.

Another was a young man who wanted to get a law degree, but because he had a reading problem he felt he needed the drugs to study. He ended up quitting law school and eventually became a successful salesman without the drugs.

Others may turn to the drugs to help them meet expectations to maintain a job and salary that allows a higher standard of living, Diller said.

"That's what it comes down to," he said. "I call the condition 'American achievement anxiety disorder.'"

The number of published papers on adult ADHD increased dramatically from 2006 through 2010, reaching 100 or more in 2 of those years, according to a tally published in 2011 in The Psychiatrist. Moncrieff co-authored the paper.

In the Beginning There Was Biederman

Joseph Biederman, MD, a psychiatrist with Harvard Medical School, was a co-author of the 2006 study that put the prevalence rate at 4.4% of adults, or about 10 million people. He has since published many more papers, all more or less supporting the findings of the 2006 study.

He bristled at the idea adult ADHD was largely a concocted disorder.

"The conspiracy theory of ADHD and other equally nonsensical ideas should be better asked from the Church of Scientology and not from a researcher clinician like myself," he wrote in an email.

Biederman, who also works for Massachusetts General Hospital, declined to be interviewed by phone and only answered a few questions by email.

He would not respond to questions about the lack of disclosure of his financial ties to the drug industry.

In addition, there were no financial disclosures listed in his 2006 paper, which was published in the American Journal of Psychiatry. That paper was partially funded by Eli Lilly. Two years later, Lilly received an FDA warning letter, which chastised the company for alleged misleading claims about its popular ADHD drug, Strattera.

The 2006 paper relied significantly on Biederman's research, citing 14 papers in which he was an author.

The conclusion that 4.4% of adults having ADHD was based on 3,199 interviews were conducted among 18- to 44-year-olds by nonmedical personnel.

Since attention deficit disorder (ADD) with or without hyperactivity was initially recognized as a disorder in children in 1980 and since then there has been a steady diagnosis creep to encompass adolescents and finally adults.

"If we are not careful, we are going to get geriatric ADHD," Conrad, the Brandeis professor and author said in an interview.

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